The invention relates to an arrangement for processing collected low-grade waste paper.
The problem of the processing and utilization of the major part of collected waste paper is attaining more and more importance in the whole civilized world. Sources of fresh wood material are already exhausted in many countries; in other countries their exhaustion is only a question of a short time. That means that any further increase in the manufacture of paper and cardboard can be accomplished substantially only by repeated utilization of collected waste paper for their manufacture.
The present trend aims primarily at the processing of wastepaper of better qualities, the demand for which is steadily increasing in the manufacture of paper. Disproportion between supply and demand are arising. This disproportion is usually solved by increasing the number of categories of collected waste paper. Each individual category is suitable for the manufacture of a certain kind of paper or cardboard.
The advantages of this kind of categorization of collected waste paper are that newly developed machines for processing waste paper can reckon with a supplied homogenous material for which they are designed, thereby providing paper of better qualities, either mechanical or visual.
A drawback of this kind of categorization is that waste paper which does not comply for any reason with given standards cannot be used at all and becomes a problem waste.
In order also to permit processing of waste paper which by its qualities does not comply with requirements to be included in a certain quality category, some large enterprises have proposed methods and arrangements for its processing.
The following patent specifications, namely the German Offenlegungsschrift No. 1,008.562 and No. 2,413,278, and U.S. Pat. No. 4,000,031 deal with the possibilities of obtaining fibers from laminated paper material. In the U.S. Pat. Nos. 3,736,223; 3,849,245 and 3,849,246 there are described possibilities of processing very contaminated waste containing paper, fats, metal, glass, bitumins, waxes and the like. Processing of waste paper of low quality is described in the German Offenlegungsschrift No. 2,413,159 and in U.S. Pat. Nos. 3,957,572 and 1,017,033 whereby for release of paper fibers and admixtures the principle of very intensive action of shearing forces in special devices is applied. The possibility of separating from the fibrous material obtained from waste corrugated cordboard two fractions according to the length of fibers is disclosed in U.S. Pat. No. 3,125,150.
A common drawback of these mentioned arrangements is that, with a simultaneous removal of unwelcome admixtures of paper, they do not permit the mechanical properties of the fibrous material obtained from waste paper to be improved. This is due to the high content of dead short fractions with an insufficient activity of good long fibers.
Under the term "low-grade collected waste paper" unclassified collected waste or the so-called "waste basket collection" is to be understood. Such waste paper contains small amounts of non-paper admixtures (sheet clips, bookbinding board, carbon paper, foamed polystyrene from corrugated board boxes, etc.) The term is not meant to comprise waste which is predominantly of specific paper types such as Al-foil coated paper, waxes paper and paper coated with hot-melts and paper/plastic laminates.
At present, the paper waste collection in Czechoslovakia amounts to about 390,000 ton per annum, of which up to 70 percent is mixed collection and only 30 percent pure paper classes. In an endeavor to raise in the future the consumption of waste paper in paper-making industry, attempts have been made to admix the low-grade waste with the high-grade one. The present invention provides a system which, due to its specific arrangement, permits the use of low-grade waste paper for this purpose by selecting good paper fibers and activizing them for further processing. The system makes it possible to gradually free paper in the form of an aqueous suspension from heavy impurities and then to disintegrate it into a fine structure, further to fractionize off unwanted fine components, activize usable fibers, separate thermoplastic materials and medium-sized impurities and, finally, to separate extra-fine contaminants. Since the invention originates from specific conditions and is designed for specific purposes (as for a large factory for processing low-grade waste paper), it solves the problem of reclaiming low-grade waste in a new and progressive plant.